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Lino M P Ramos

Publications and source records attributed to Lino M P Ramos.

7 recordsLinked to original sources
PubMed2005

Altered flow territories after extracranial-intracranial bypass surgery.

OBJECTIVE: To prevent stroke after carotid sacrifice and to augment cerebral perfusion in patients with internal carotid artery (ICA) occlusion, high-flow extracranial-intracranial (EC-IC) bypass operations are performed. Although the function and efficacy of the bypass is monitored during surgery, the postoperative flow through the bypass is significantly lower than the flow in the contralateral ICA. Thus far, it is unknown whether decreased bypass flow is caused by a low tissue perfusion or by a relatively small flow territory. METHODS: Seven patients, four with an atherosclerotic ICA occlusion and three with a giant aneurysm of the ICA, were investigated; each underwent a high-flow EC-IC bypass and permanent occlusion of the ICA. Cerebral blood flow was measured with arterial spin labeling perfusion magnetic resonance imaging. Separate flow territory mapping of the EC-IC bypass, contralateral ICA, and posterior circulation was performed with selective arterial spin labeling magnetic resonance imaging. RESULTS: No significant difference was found in cerebral blood flow between the hemisphere ipsilateral to the EC-IC bypass (70.9 +/- 11.3 ml/min/100 g tissue), contralateral to the EC-IC bypass (71.9 +/- 14.3 ml/min/100 g tissue), and comparable findings in 50 healthy control participants (69.1 +/- 17.5 ml/min/100 g tissue). Paired analysis of the individual flow territories demonstrated a 15% volume reduction (P = 0.018) in flow territory of the EC-IC bypass compared with the contralateral side. CONCLUSION: In the present study, we demonstrate the feasibility of selective arterial spin labeling magnetic resonance imaging for clinical follow-up of patients after high-flow EC/IC bypass surgery, providing both information on flow territories and the level of regional cerebral blood flow.

Adult↗
PubMed2004

Björk-Shiley convexoconcave valves: susceptibility artifacts at brain MR imaging and mechanical valve fractures.

PURPOSE: To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Björk-Shiley convexoconcave (BSCC) valves. MATERIALS AND METHODS: MR images of the brain were obtained in 58 patients with prosthetic heart valves: 20 patients had BSCC valve replacements, and 38 had other types of heart valves. Two experienced neuroradiologists determined the presence or absence of susceptibility artifacts in a consensus reading. Artifacts were defined as characteristic black spots that were visible on T2*-weighted gradient-echo MR images. The statuses of the 20 explanted BSCC valves-specifically, whether they were intact or had an outlet strut fracture (OSF) or a single-leg fracture (SLF)-had been determined earlier. Number of artifacts seen at brain MR imaging was correlated with explanted valve status, and differences were analyzed with nonparametric statistical tests. RESULTS: Significantly more patients with BSCC valves (17 [85%] of 20 patients) than patients with other types of prosthetic valves (18 [47%] of 38 patients) had susceptibility artifacts at MR imaging (P =.005). BSCC valve OSFs were associated with a significantly higher number of artifacts than were intact BSCC valves (P =.01). No significant relationship between SLF and number of artifacts was observed. CONCLUSION: Susceptibility artifacts at brain MR imaging are not restricted to patients with BSCC valves. These artifacts can be seen on images obtained in patients with various other types of fractured and intact prosthetic heart valves.

Adult↗
PubMed2003

Direction of flow in posterior communicating artery on magnetic resonance angiography in patients with occipital lobe infarcts.

BACKGROUND AND PURPOSE: In some people the blood supply to the posterior cerebral artery occurs partly or even exclusively via the carotid system. This anatomic configuration may influence the risk of occipital lobe infarction. We studied the presence and direction of flow in the posterior communicating artery (PCoA) in patients with an occipital lobe infarct and in healthy controls. METHODS: Forty-seven patients with an occipital lobe infarct were studied by MR angiography, as well as 50 young healthy controls. Special attention was paid to the presence of a PCoA and, if present, to the direction of flow. RESULTS: Significantly fewer patients than controls had an exclusive blood supply to the posterior cerebral artery via the carotid system, in both the affected (4% versus 17%; 95% CI of difference, 4% to 22%) and unaffected hemispheres (5% versus 17%; 95% CI of difference, 3% to 22%). Patients also less often had a patent PCoA with anteroposterior flow than controls (affected hemisphere, 8% versus 22%; unaffected hemisphere, 12% versus 22%; 95% CI of differences, 3% to 25% and -2% to 23%, respectively). With analysis at the level of individuals, significantly more patients showed no anteroposterior flow through the PCoA in either hemisphere than controls (79% versus 42%; 95% CI of difference, 19% to 55%). CONCLUSIONS: Supply of the posterior cerebral artery by the carotid system occurs less often in patients with an occipital lobe infarct than in healthy controls. The same was true for the unaffected hemisphere of patients, which suggests that the anatomic difference represents a causal factor (fewer collateral pathways after occlusion of the posterior cerebral artery or its branches) rather than a consequence (redistribution of blood flow after occipital infarction).

Adult↗
PubMed2003

Hemodynamic compensation via an excimer laser-assisted, high-flow bypass before and after therapeutic occlusion of the internal carotid artery.

OBJECTIVE: High-flow, extracranial-intracranial (EC-IC) bypass operations are performed to prevent strokes among patients with giant aneurysms who cannot tolerate internal carotid artery (ICA) occlusion. However, the volume flow through the bypass, compared with preoperative ICA flow, has not been evaluated for any type of bypass. We describe a prospective case study that tested the ability of the high-flow EC-IC bypass to replace the volume flow of the ipsilateral ICA after deliberate ICA occlusion. METHODS: Seven consecutive patients with giant aneurysms of the ICA who experienced test occlusion failure underwent nonocclusive, excimer laser-assisted, EC-IC bypass surgery before permanent ICA occlusion. Volume flow values in the ICAs, the basilar artery, the EC-IC bypass, and the middle cerebral arteries were measured with magnetic resonance angiography. RESULTS: No significant changes in volume flow to the ipsilateral and contralateral hemispheres were observed after bypass surgery and therapeutic ICA occlusion. Before bypass surgery, the volume flow through the ipsilateral ICA was 243 +/- 74 ml/min, that through the contralateral ICA was 264 +/- 32 ml/min, and that through the basilar artery was 141 +/- 43 ml/min. After bypass surgery and therapeutic occlusion of the ipsilateral ICA, the volume flow through the bypass was 199 +/- 72 ml/min, that through the contralateral ICA was 303 +/- 82 ml/min, and that through the basilar artery was 153 +/- 72 ml/min. No significant preoperative versus postoperative changes in middle cerebral artery flow were observed on either side. CONCLUSION: The flow through the high-flow EC-IC bypass was able to replace the volume flow of the ipsilateral ICA after deliberate ICA occlusion for the treatment of giant aneurysms.

Adult↗
PubMed2002

Blood supply of the posterior cerebral artery by the carotid system on angiograms.

BACKGROUND AND PURPOSE: Occipital lobe infarcts are traditionally attributed to vertebrobasilar disease. However, anatomical studies indicate that in some people the supply of the posterior cerebral artery is via the carotid system. We investigated how often such a developmental variant in the cerebral blood supply was present during life. METHODS: We retrospectively studied 212 conventional four-vessel cerebral angiograms. Eighteen subjects were excluded beforehand, because of vascular abnormalities causing important hemodynamic changes. We determined whether a fetal variant was present, and in other cases whether there was a functioning posterior communicating artery. RESULTS: In 11 % of hemispheres the posterior cerebral artery was exclusively supplied by the internal carotid artery; in a further 46 % of hemispheres the internal carotid artery might contribute, via a patent posterior communicating artery. In 75 % of subjects the internal carotid artery contributed in at least one hemisphere to the blood flow of the posterior cerebral artery. CONCLUSIONS: The implication of our findings is that an occipital lobe infarct can be caused by ipsilateral carotid disease in a proportion of cases between 10 and 60 %. This implies that carotid endarterectomy might be beneficial in some patients with severe carotid stenosis and infarction in the territory of the posterior cerebral artery.

Adolescent↗
PubMed1994

Electrode positioning in thoracic percutaneous partial rhizotomy: an anatomical study.

The present study was undertaken to clarify if needle positioning in percutaneous partial rhizotomy in the thoracic area based on bony landmarks and guided by fluoroscopic control leads to adequate placement in or at the targeted nervous tissue, i.e., the dorsal root ganglion (DRG), and to determine if needle localization by CT is more reliable than by fluoroscopic control. An investigation was performed in 2 cadavers, simulating the clinical setting as much as possible. At the levels T1-T8 a drill hole was made in the vertebral arc with a Kirschner wire. At the levels T9-T12 the "classic" dorsolateral technique was used. In 46 procedures the position of the needle tips was compared using hard copies of the fluoroscopic images, CT images at 1.5 mm intervals, surface photographs, and stained 25 microns sections obtained by a multirange heavy duty cryomicrotome. The position of the DRG in the foramen, and its size, were measured. In the sections, considered as the "golden standard", in 28 cases (60.9%) the needle tip was found in the DRG and in the extradural dorsal root in 14 cases (30.4%). In 4 cases (8.7%) no nervous tissue was encountered. In 8 of 32 "drill hole procedures" the facet joint was pierced. No accidental pleural puncture occurred in any of the procedures. The needle position was imaged more accurately by fluoroscopy. It is concluded that fluoroscopic control is a reliable guide to needle placement in percutaneous partial rhizotomy and permits standardization of the technique with the help of bony landmarks.

Aged↗